Research Of Hydrothermal Preparation For Lead Strontium Titanate Ceramics

The ferroelectric materials has been researched for about a century, includes theinterconnection of strain, polarization, and temperature. With the development ofelectronic information technology and other importantfields, some new requirementswaiss proposed, about this material such as the adaptability of environments, Therefore ithas recently become a hot topic in the currently research.Lead strontium titanate ceramics is a new type of ferroelectric ceramic materials,which integrates the superiority of strontium titanate (ST) and lead titanate, and It has acharacteristic property of resistance-temperature, that is, at the same time possess apositive temperature coefficient (PTC)-negative temperature coefficient (NTC).Consequently, it has composite thermal function which other materials don’t have. Thus itis often used as the thermal ceramic, which is suitable for miniaturization and integrationof electronic technology direction.At present, the strontium titanate lead in electronic ceramic powder was mainlyprepared by solid phase method, co-precipitation method in the liquid phase, sol-gelmethod, and ultrasonic chemical method etc. In the method of solid phase it presentedconsiderable problems such as mixed-sintering of the solid powders, the composition ofmixed uneven, serious pollution, and high sintering temperature.In the method of coprecipitation,it was relatively difficult to accurately prepare thesolution, besides operating conditions are tedious; In the method of sol-gel it has longreaction time and the product was easy to crack; In the method of ultrasonic chemical,large-scale industrial applications are rarely, and the particles was easy to assemble dueto inappropriate ultrasonic frequency and temperature. In the method of hydrothermal inthe liquid phase, not only is the response equipment simple, but also it was easy foroperation, Notablely the finished products of strontium titanate lead powder were readilyobtained by the hydrothermal reaction under the temperature of473K. Foreign countrieshave been strontium lead titanate hydrothermal preparation method, and thereare few studies in our country.The lead volatilize so readily to influence its function and structure t hat they mustbe protected from high temperature Moreover,the manufacturing process were necessaryto simplify and the small particle of powders and different type of crystals were finally prepared.According to the hydrothermal method, it can reduce the volatilization of lead,while the operation is simple, the change of preparation conditions is easy and so on,Therfore hydrothermal method was used to prepare strontium titanate lead powder body inthis paper.The main content of this paper includes:1. IntroductionThe main preparation methods of the strontium titanate lead powder body wereintroduced, and the advantages and disadvantages of various methods were compared.2. Preparation and characterization of strontium titanate lead powder bodyThe strontium titanate lead powder body was prepared by hydrothermal method andthe condition effects on the reaction were discussed respectively such as lead strontiumratio, reaction time, reaction concentration, and reaction temperature.The experimental results show that the strontium content in the powder affects thecrystal structure.With the increase of strontium content, strontium titanate lead crystal wastransformed from tetragonal into the cubic phase, and strontium replaces the position ofthe lead, which provided the foundation for the future preparation of the desired crystalform.In the same reaction conditions, with the growth of the reaction time, the decrease ofreaction concentration, the increase of reaction temperature, the crystal particle sizeincreased.Strontium titanate lead powder body was characterized by XRD, SEM. Thepreparation conditions were investigated according to the characterization results. Basedon systematically further investigation, different diameters of strontium titanate leadpowder body were obtained by controlling the hydrothermal conditions. And thehydrothermal synthesis conditions of strontium titanate lead were concluded.3. The hydrothermal synthesis mechanism of strontium titanate leadThe precursors of strontium titanate lead firstly dissolve under hydrothermalconditions, and then positive and negative ions react with each other, to generate insolubleproduct.